U.S. patent number 7,259,372 [Application Number 11/135,076] was granted by the patent office on 2007-08-21 for processing method using probe of scanning probe microscope.
This patent grant is currently assigned to SII NanoTechnology Inc.. Invention is credited to Osamu Takaoka, Shigeru Wakiyama, Naoya Watanabe, Masatoshi Yasutake.
United States Patent |
7,259,372 |
Takaoka , et al. |
August 21, 2007 |
Processing method using probe of scanning probe microscope
Abstract
A processing method uses a probe of a scanning probe microscope.
A fine marker is formed in a processing material by thrusting the
probe, which is made of a material harder than the processing
material, into a portion of the processing material disposed in the
vicinity of an area of the processing material to be processed by
the probe during a processing operation. A position of the fine
marker on the processing material is detected during the processing
operation. A drift amount of the area of the processing material is
calculated in accordance with the detected position of the fine
marker. A position of the area of the processing material is
corrected in accordance with the calculated drift amount.
Inventors: |
Takaoka; Osamu (Chiba,
JP), Yasutake; Masatoshi (Chiba, JP),
Wakiyama; Shigeru (Chiba, JP), Watanabe; Naoya
(Chiba, JP) |
Assignee: |
SII NanoTechnology Inc.
(JP)
|
Family
ID: |
35424160 |
Appl.
No.: |
11/135,076 |
Filed: |
May 23, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050263700 A1 |
Dec 1, 2005 |
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Foreign Application Priority Data
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May 25, 2004 [JP] |
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2004-154059 |
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Current U.S.
Class: |
250/309; 850/33;
430/5; 250/306; 310/317; 204/192.32 |
Current CPC
Class: |
G03F
1/72 (20130101); B82Y 10/00 (20130101); G01Q
70/04 (20130101); G01Q 10/06 (20130101); G01Q
80/00 (20130101) |
Current International
Class: |
G01N
23/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Berman; Jack I.
Assistant Examiner: Hashmi; Zia R.
Attorney, Agent or Firm: Adams & Wilks
Claims
What is claimed is:
1. A processing method using a probe of a scanning probe
microscope, comprising the steps of: forming a fine marker in a
material to be processed by thrusting a probe made of a material
harder than the material to be processed into a portion of the
material to be processed that is in the vicinity of an area of the
material to be processed by the probe during a processing
operation; detecting a position of the fine marker during a
processing operation; calculating a drift amount of the area of the
material to be processed in accordance with the detected position
of the fine marker; and correcting a position of the area of the
material to be processed by an amount corresponding to the
calculated drift amount.
2. A processing method using a probe of a scanning probe microscope
according to claim 1; wherein the detecting step comprises the step
of detecting the position of the fine marker in accordance with a
center of gravity of the fine marker.
3. A processing method using a probe of a scanning probe microscope
according to claim 1; wherein the probe comprises a probe of a
scanning tunnel microscope; wherein the processing material
comprises a conductive material; and wherein the calculating step
comprises the step of calculating the drift amount by tracking a
position of a deepermost portion of the fine marker with the probe
using an atom-tracking method while applying a tunneling current
between the fine marker and the probe.
4. A processing method using a probe of a scanning probe microscope
according to claim 1; wherein the fine marker has a cross-shaped or
L-shaped pattern; further comprising the steps of storing the
pattern shapes of the fine marker in advance, observing the pattern
of the fine marker during the processing operation, and matching
the observed pattern of the fine marker with the stored pattern
shapes; and wherein the calculating step comprises calculating the
drift amount of the fine marker in the X direction and Y direction
thereof, and the correcting step comprises correcting the position
of the area to be processed by an amount corresponding to the
calculated drift amount.
5. A processing method using a probe of a scanning probe
microscope, comprising the steps of: forming a plurality of fine
markers in a material to be processed by thrusting a probe made of
a material harder than the material to be processed into portions
of the material to be processed disposed in the vicinity of an area
of the material to be processed during a processing operation;
obtaining in advance a positional relation between positions of the
fine markers and a position of the area of the material to be
processed; detecting the positions of the fine markers during a
processing operation; and obtaining by affine transformation of the
fine markers the position of the area of the material to be
processed that has the same position relation with the detected
positions of the fine markers as the position relation obtained in
advance to thereby correct a drift of the position of the area of
the material to be processed.
6. A processing method using a probe of a scanning probe microscope
according to claim 5; wherein the forming step comprises the step
of forming the plurality of fine markers in the material to be
processed at positions surrounding the position of the area of the
material to be processed.
7. A processing method using a probe of a scanning probe microscope
according to claim 1; further comprising the step of storing in
advance a preselected pattern shape of the fine marker, observing
the pattern of the fine marker during the processing operation, and
matching the observed pattern of the fine marker with the stored
preselected pattern shape; and wherein the calculating step
comprises calculating the drift amount of the fine marker in the X
direction and Y direction thereof; and the correcting step
comprises correcting the position of the area to be processed by an
amount corresponding to the calculated drift amount.
8. A processing method using a probe of a scanning probe microscope
according to claim 5; wherein the plurality of fine markers
comprise three or more fine markers.
9. A processing method using a probe of a scanning probe microscope
according to claim 6; wherein the plurality of fine markers
comprise three or more fine markers.
10. A processing method comprising: forming a fine marker in a
processing material by thrusting a probe made of a material harder
than the processing material into a portion of the processing
material disposed in the vicinity of an area of the processing
material to be processed by the probe during a processing
operation; detecting a position of the fine marker on the
processing material during a processing operation; calculating a
drift amount of the area of the processing material in accordance
with the detected position of the fine marker; correcting a
position of the area of the processing material in accordance with
the calculated drift amount; and processing the area of the
processing material at the corrected position thereof using the
probe.
11. A processing method according to claim 10; further comprising
the steps of repeating the detecting, calculating, correcting and
processing steps a preselected number of times.
12. A processing method according to claim 10; wherein the
detection step comprises the step of detecting the position of the
fine marker in accordance a center of gravity of the fine
marker.
13. A processing method according to claim 10; wherein the probe
comprises a probe of a scanning tunnel microscope and the
processing material comprises a conductive material.
14. A processing method according to claim 13; wherein the
calculating step comprises the step of calculating the drift amount
by tracking a position of a deepermost portion of the fine marker
with the probe using an atom-tracking method while applying a
tunneling current between the fine marker and the probe.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a processing method using a probe
of a scanning probe microscope and, more specifically, to a method
of correcting drift of a processing position.
A microprocessing technology on the order of nanometer is required
for improvement of level and degree of integration of functions,
and research and development regarding processing technologies,
such as local anodic oxidation or fine scratch processing using a
scanning probe microscope (SPM), has been extensively carried out.
Not only has microprocessing become important, but also processing
with high degree of accuracy is now increasingly required.
In order to improve the accuracy of microprocessing, not only is
the microprocessing capability or a highly accurate positioning
technology important, but also reduction or correction of drift,
such as thermal drift unavoidably generated during processing, have
to be performed since processing using the SPM takes time. As a
method of correcting drift on the order of 1 nm, a method of
correcting a processing range in real time using a laser
interferometer has been employed. The method using the laser
interferometer has an advantage of real time, but since the amount
of displacement of a mirror mounted to a stage is observed instead
of the position near the processing point, there may be the case in
which the amount of drift correction is different from that
actually required. In particular, when the sample is a large sample
such as a photomask or a wafer, the distance from the mirror and
the actual processing point increases, and hence the tendency of
being different from the actually required amount of drift
correction increases correspondingly. When the temperature between
the sample and the mirror is different, the laser interferometer
cannot measure the thermal drift of the sample accurately, and
hence the processing is performed after having waited until the
sample and the mirror are thermally balanced.
In the processing using the SPM, the influence of the drift is
reduced by performing the drift correction with the measured value
of the laser interferometer or by repeating the process of
observing the area including the processing point in an observation
mode in the course of processing and then redefining the processing
area before restarting the processing. In the method of observing
in the observation mode and redefining the processing area before
restarting the processing, if the processing area is large and
observation is performed to an extent sufficient for the drift
correction, it takes long time for observation, and hence there may
arise a difference between the result of observation and the
actually required amount of the drift correction, and in addition,
the throughput is deteriorated. When the observation is made
roughly, it does not take long time, but the accuracy of drift
correction is disadvantageously deteriorated. Although a method of
observing a characteristic pattern at the portion near the
processing point in the course of processing and then performing
the drift correction by pattern matching is also conceivable, there
is a problem that there is no guarantee that a pattern which can be
used for pattern matching both in X-direction and Y-direction
always exists at the portion near the processing point.
In the case of defect correction of a photomask or manufacturing a
sample for a transmission electron microscope using a focused ion
beam, a method of processing including steps of opening small holes
with a concentrated ion beam at positions near the processing point
as drift markers, selectively scanning the area of several
micrometers including small holes which are formed regularly by
interrupting the processing in the course of the processing,
obtaining the drift amount from displacement of the center of
gravity of the small holes, and correcting the range of processing
is employed, whereby the processing with high degree of accuracy of
20 nm or below is realized (for example, JP-B-5-4660 (P. 2, FIG.
11)). However, in the processing using the SPM, such a method has
not been employed.
An atom-tracking method is developed as a method of tracking a
substance of an atomic level size on the surface with atomic level
accuracy. The atom-tracking method is a method developed for the
scanning tunneling microscope (STM) which enables tracking of
surface diffusion of an atomic size atom, in which a probe is
rotated at a high speed substantially in radius of an atom in a
horizontal plane, detecting a varied signal which depends on the
position of a tunneling current by a lock-in amplifier, and giving
feed-back to X-Y scanning (for example, B. S. Swartzentruber. Phys.
Rev. Lett. 76 459-462(1996)), and has a potential for correcting
the drift of 1 nm level in real time. However, it has not been used
for the aforementioned drift correction.
The present invention is intended to enable processing with high
degree of accuracy in a processing machine in which a scanning
probe microscope is applied.
SUMMARY OF THE INVENTION
In a processing method using a probe of a scanning probe
microscope, fine markers are formed by thrusting a probe, which is
harder than material to be processed, into a portion near the area
to be processed by the probe, the positions of the fine markers are
detected in the course of the processing using the probe, the drift
amount is calculated, the position of the area to be processed is
corrected by an amount corresponding to the drift amount, and the
processing is restarted. Detection of the positions of the fine
markers is performed based on the position of the center of gravity
or the deepermost portion.
The steps of detecting the fine markers, calculating the drift
amount, and processing in the area corrected by the drift amount
are repeated for achieving the processing with a high degree of
accuracy.
When the magnification or rotation is different for each time of
image observation, the fine markers are formed at three or more
positions by thrusting the probe, which is harder than the material
to be processed, into positions which surround the processing area,
and the positional relation between the fine markers and the
processing area is obtained. Then, steps of obtaining the position
of the processing area with respect to the respective fine markers
by affine transformation in the course of processing, calculating
the drift amount of the processing area, and restarting the
processing in the processing area where the drift amount is
corrected are performed. The process of detecting the 3 or more
fine markers, calculating the drift amount, and processing in the
area where the calculated drift amount is corrected are repeated to
achieve the processing with high degree of accuracy. The affine
transformation itself is a method which is generally used in the
fields of mathematics and image processing.
The atom-tracking method developed for tracking the surface
diffusion of the atom is used for tracking the change of the
position of the markers formed for drift correction due to drift.
The multi probe SPM processing machine performs processing while
tracking the markers using one of the probes via the atom tracking
method, feeding back the result of tracking in real time to the
scanning area (processing area) for other probe for processing, and
correcting the drift. In other words, it searches for the
deepermost portion of the fine markers by rotating the probe
substantially in radius of atom at high speed in a horizontal plane
and obtaining the point where the largest tunneling current is
detected while flowing the tunneling current between the probe and
the sample, and determines this point as a maker position.
Consequently, the deepermost portion at the marker positions is
accurately obtained, whereby more accurate processing is
enabled.
Not only the pattern formed simply by thrusting the probe, but a
pattern which can indicate displacement in the X-direction and
Y-direction by thrusting the probe is formed, then the pattern
position and the pattern form are stored in advance. Then, matching
with the stored pattern is performed by observing the area
including the formed pattern in the course of processing, the drift
amount is calculated in the X and Y directions, and the result is
fed back to the scanning area (processing area) of the probe for
processing.
By using the probe formed of hard material such as diamond, the
fine markers can be formed on most materials by thrusting the
probe. By using the probe having a pointed end, the fine markers
can be formed and hence the drift correction with high degree of
accuracy is achieved.
Even when the magnification or the rotation is different for each
time of image observation, further accurate drift correction can be
achieved by the drift estimation in the processing area by the
affine transformation of the markers at three or more
positions.
Since the drift at the portion near the processing point can be
detected with high degree of accuracy by applying the atom-tracking
method to the fine hole markers provided on the conductive portion
near the processing point, the drift correction with high degree of
accuracy is enabled. Also, due to the high-speed trackability of
the atom-tracking method, the real time correction is enabled.
By forming the pattern which can indicate displacement in the X
direction and the Y direction like a cross-shape or L-shape, the
drift amount can be calculated with high degree of accuracy by
pattern matching, thereby achieving the accurate drift
correction.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A-1C are schematic cross-sectional views showing a
characteristic of the present invention in the most understandable
manner.
FIG. 2 is an explanatory plan view showing a case in which a drift
is corrected by three or more drift markers.
FIG. 3 is an explanatory schematic cross-sectional view showing a
case of correcting a drift by an atom-tracking method using one
scanning tunneling microscope probe of a multi-probe scanning probe
microscope in real time and fabricating with another probe.
FIG. 4 is an explanatory plan view showing a case of correcting the
drift by forming drift markers by scanning the probe in a state in
which a probe, which is harder than material to be processed, is
thrust, and performing the pattern matching therewith.
DETAILED DESCRIPTION OF THE INVENTION
A case in which the invention is applied to removal of defect of
excessive pattern of the photomask will be described as an example
of the present invention below.
As shown in FIGS. 1A-1C, a drift is corrected by forming fine
markers 5 by thrusting a probe 4 into shield film 2 on glass
substrate 1, which is harder than material to be processed, at the
portion near a black defect 3, which is a processing area as shown
FIG. 1A, detecting the position of the markers 5 in the course of
processing, calculating the drift amount as shown in FIGS. 1B and
1C, and feeding back the calculated drift amount to the processing
area.
When the magnification or the rotation is different for each time
of image observation, the fine markers 5 are formed at three or
more positions by thrusting the probe 4, which is harder than the
material to be processed, at the portion near the processing area
as shown in FIG. 2, and the positional relation between the fine
markers 5 and the processing area is obtained in advance. Then, the
positions of the fine markers are detected in the course of
processing with probe 4 scanning scanning area 6, and the position
of the processing area in the aforementioned positional relation is
obtained by the affine transformation. Processing is performed by
correcting the position of the processing area drifted as described
above. The drift correction of the fine markers can be performed
more accurately by arranging the fine markers so that the
processing area 3 is surrounded by lines connecting the fine
markers.
An image including the area to be processed is obtained by an
atomic force microscope or the like, and the processing area is
determined from the obtained image. As shown in FIG. 3, the markers
5 on the order of several ten nanometers to be tracked by the atom
tracking method are formed by thrusting the probe 4, which is
harder than the material to be processed, into the conductive
material near the processing area. Then, processing with high
degree of accuracy such as anodic oxidation or scratch is performed
by tracking deepermost portions of the markers 5 by one of the STM
probes 7 of the SPM processing machine having a number of probes by
the atom-tracking method, feeding back the amount of movement to
the scanning range (processing area) of the probe for processing in
real time, and correcting the drift.
As a matter of course, drift correction with high degree of
accuracy is also achieved not only by forming the markers 5 formed
simply by thrusting the probe 4, but also by forming a fine
cross-shaped or L-shaped pattern 8 by scanning the probe 4, which
is harder than the material to be processed, in the X-direction and
the Y-direction in a state of being thrust as shown in FIG. 4, and
performing the pattern matching with these patterns as the drift
markers to correct the drift in the X-direction and
Y-direction.
* * * * *